Telephone system



Feb. 23, 1932. w. r. HAINES TELEPHONE SYSTEM Filed June 5, 1931 13 Sheets-Sheet 1 IN VE' N TOR w r HAINES A TTORNEY Feb. 23, 1932. w. T. HAINES TELEPHONE SYSTEM 13 Sheets-Sheet 2 Filed June 5, 1931 Filed June 5, 1931 13 Sheets-Sheet 3 gwo W. 7'. HA INES MGM fab k ATTORNEY Feb. 23, 1932. w. 'r. HAINES TELEPHONE SYSTEM Filed June 5, 1931 15 Sheets-Sheet 4 lNl/EN TOR W. I HA INES A TTORNEY 1 Feb. 23, 1932.

W. T. HAINES TELEPHONE SYSTEM Filed Juhe 5, 1931 15 Sheets-Sheet 5 A TTO/PNEV Feb. 23, 1932. w. T. HAINES TELEPHONE SYSTEM Filed June 5, 1931 13 Sheets-Sheet 6 INVENTOI? W. 7? HAINES BY i @Q ATTORNB Feb. 23, 1932. w. 1*. HAINES TELEPHONE SYSTEI htzb INVENTOR I W. 7". HA INES A TTORNEY W- T. HAINES TELEPHONE SYSTEM Filed June 5, 1931 FIG.8

13 Sheets-Sheet 8 INVENTOR W 7? HAINES.

A TTORNEY Feb. 23, 1932. w. 'r. HAINES TELEPHONE SYSTEM 13 Sheets-Sheet Filed June 5, 1931 INVENTOR M. 7'. HA INES ATTORNEY Feb. 23, 1932.

w. T. HAINE S TELEPHONE svs'rnu -13 Sheets-Sheet 10 Filed June 5, 1931 INVENTOR W. 7'. HAINES ATTORNEY Feb. 23, 1932.

w. T. HAINES TELEPHONE SYSTEM 1s Sheets- Sheet 11' Filed June 5, 1931 INVENTOR W TTHAINES 9Q um A TTORNEY Feb. 23, 1932. w. 1-. HAINES 3 5 TELEPHONE SYSTEM Filed June 5. 1931 13 Sheets-Sheet 12 uvvzw r01? W. 7'. HAINES Hm h.

A T TORNEY Patented Feb. 23, 1-932 UNITED? STATES PATENT OFFICE WILLIAM '1. HAINES, OF MOUNTAIN LAKES,-NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK TELEPHONE SYSTEM Application .filed J'une 5, 1931. Serial No. 542,436.

This invention relates to telephone systems and more particularly to line indicating devices used in such systems.

In telephone systems employing line extending switches for completing a part of a telephone connection, it becomes necessary on certain types of calls, such as a toll call, to supply the operating company with information as to the identity of the calling line number. Under such circumstances the line extending switches, controlled by the calling subscriber, serve to connect the line to an operators position where facilities exist for further extending the connection after the operator has been apprised by the calling subscriber of the identity of the calling line number. This informationis necessary in order to permit the operating company to bill the calling station for the toll call. Facilities are usually provided for verifying the line number as given by the calling subscriber, so' that the operating company will make no error in properly charging the toll call to the station from which the call is made.

At the present time number checking is being-accomplished in divers ways, among which there is the well known checking multiple method whereby the operator, upon being apprised of the calling line number, applies the tip conductor of a cord to a sleeve conductor of the calling line in the-checking multiple in which all the lines in the office terminate; the method whereby the operator, after having been given the number by the subscriber, sets a train of switches to select the calling line as given by the subscriber and thereafter impresses a tone over the sleeve conductor of the extended connection, the tone circuit being closed over the switches set by the operator and returning by way of the switches set by the subscriber so that, if the line number as given by the subscriber checks with the line terminal to which the operator has set the switches, the operator will hear the tone which was impressed over the line conductor; and other methods for causing a lamp display of the calling line number, the lamp display circuit being set by trains of impulses characteristic of the calling line.

These and other means have been used with varying degrees of success but either require the operator to obtain the line designation from the calling subscriber thereby slowing down the service or involving a large amount of equipment of a character difiicult to maintain. The object of the invention is, therefore, to provide a more direct and efficient method for determining the calling subscribers line numbers; the said means being of a structure which is both reliable in operation and economical to maintain.

The apparatus and organization of circuits described in the present invention is a means for number checking based upon the use of a positive hunting circuit for locatin an identified conductor of the calling line and thereafter causing a corresponding display of the line number on an indicating device before the operator. invention, therefore, one specific embodiment of which is disclosed herein by way of illustration this is accomplished in the following improved manner: Each operators position capable of extending calling sub-' scribers lines to toll points and for which a verification of the calling line number is necessary, is provided with four sets of re lays and lamps for the display of a fourdigit number and an additional set for displaying the class of line. A testing circuit which is common to all such positions and to all the subscribers lines in the ofiice is used.-

By the use of a lock-out circuit under the control of a key at each such position only one pc sition at a time has accessibility to the testing circuit. Under such circumstances, it is necessary that the speed of operation be high, that is, the holding time of. the common test circuit should be very small so as In accordance with the to provide all operators with facilities for s using sible.

The testing circuit comprises an organi zation of groups of multi-contact srelays arranged in a cascade formation and other controlling relays. Each subscribers line of the oflice is provided with a multiple conthe common test circuit asfast as posnection from its sleeve conductor which extends as a test conductor to a particular con tact of a multi-contact relay in the first group of the cascade. Through the operation of the controlling relays the multi-contact relays are so operated as to select the thousands, hundreds and tens groups in whlch is included the test conductor of a calling line and finally the test conductor of the calling line itself.

When a subscriber has extended a connection to the recording operators position the operator, in response to the call, depresses a position checking key and if the test circuit is available at the time, it is taken into use and all other operators positions are locked out from access thereto. A source of alternating current is then connected over the connection established from the subscribers line and extended to the multiple test conductor of the calling line, establishing thereon a test potential which is instrumental in causing the test circuit to select that par ticular calling line. WVhen the test circuit has functioned to select the calling line, registers at the operators position are selectivelyoperatcd to indicate on banks of lamps controlled thereby the thousands, hundreds, tens and units digits of the calling line and the indication of the class of service to which the calling line is entitled. The operator after noting the displayed line number opcrates a release key which, in turn, extinguishes the lamps which have displayed the line number, the test circuit having auto matically restored to normal. 1

Since the quantity of alternating current which may be applied over the sleeve conductor of the established connection to the multiple test conductor is limited by impedance drains shunted at a number of oints in the circuit extending from the callmg subscribers line to the operators position, the energy available at the test conductor of the calling line in the test circuit is not sufficient to operate a test relay when its winding is directly connected to the sleeve conductor of such a line. For this reason, the test relays used in the test circuit of the present invention to detect the alternating current are each connected through a thermionic amplifier and operate over a circuit controlled through the space current thereof when the grid element responds to the alternating potential.

A clearer conception of the scope and purpose of the invention can be obtained from a consideration of the following description and attached drawin s in which,

Fig. 1 shows one o a group of subscribers lines together with the line and trip circuit common to the group of lines which serve to control a start circuit;

Fig. 2 shows the start circuit serving a plurality of groups of lines:

1926, as is necessary for the present invention.

Fig. 3 shows a line finder-district selector circuit for extendin the calling line to subsequent selectors and other types of outgoing trunks, such as a trunk to the recording operators position;

Fig. 4 shows one of a plurality of link circuits serving the start circuit of Fig. 2 and having access to a plurality of line finder district selector circuits such as shown in Fig. 3. A portion of two other links is shown;

Fig. 5 shows such )arts of the circuits of the sender disclosed in Patent 1,589,402 granted to O. H. Kopp and dated June 22, an understanding of The designation of the apparatus in Fig. 5 is identical with that of the same apparatus in the sender of the above mentioned patent;

Fig. 6 is the calling line test circuit lockout control circuit at one of the recording positions;

Fig. 7 is the line display circuit at a record ing operators position;

Fig. 8 shows a trunk from the district selector frame to the recording position;

Fig. 9 shows the toll cord and cooperating o erators telephone circuit, schematically s iown, at such position;

Figs. 10, 11, 12 and 13 show the common calling line test circuit;

Fig. 14 shows the manner in which Figs. 1 to 13 inclusive should be arranged with re spect to each other in order to disclose the invention completely.

When the subscriber at substation 100 removes his receiver from the switchhook a circuit is closed for line relay 101 extending from battery and resistance through that relay, inner contacts of relay 102 over the subscribers loop to ground at the outer contacts of relay 102. Relay 101 operates and closes a circuit from battery, resistance 104, through the winding of relay 103 to ground at the outer contact of relay 101.

The operation of relay 103 closes a circuit from battery, resistance 105 to ground at the outer right contact of relay 103. This circuit is in shunt of the winding of relay 106, which relay serves the second sub-group of the group to which line 100 belongs, thus preventing the extension of a call from that subgroup, while the trip circuit is in use with line 100. The operation of relay 103 also closes a circuit from battery, through the winding of relay 200, conductor 133, outer left contact of relay 107, outermost left contact of relay 103 to ground. In addition, relay 103 closes a circuit from battery, over the back contact of relay 201, conductor 130, right winding of trip relay 108, inner left contacts of relay 107, innermost left contacts of relay 103, left contacts of relay 109 to ground.

Relay 108 operates in this circuit and closes a locking circuit for itself from ground, right contact of relay 109, left winding and inner left contact of relay 108, Over the inner left back contact of the trip relays of the other groups of lines, conductor 129, right winding of start relay 201 to battery. Relay 201 operates in this circuit. A circuit is now closed for relay 110 extending from battery through the winding of relay 110, inner right contact of relay,108, conductor 128, to ground at the outer right contact of relay 201. Relay 110 locks in an obvious circuit to ground at the left back contact of relay 109. Relay 108, together with relay 103 prepares a circuit from ground on the outer contact of relay 110, outer left front contact of relay 108, inner right contact of relay 103, conductor 131, left back contact of relay 202, outer left back contact of relay 203, conductor 206, upper contact of cam 401, upper contact of cam 402, brush461 and its associated terminal, conductor 378, upper contacts of cam 301, wind ing of relay 302, to battery, assuming that the line finder-of Fig. 3 had been allotted for use by the switch 460 and the sequence switch 300 is therefore standin in position 2.

The operation of relay 108 also closes a circuit from ground over its outer right contact, through the winding of the trip magnet 303, serving the group of lines in which line w front contact of relay 302 toground. Under 100 appears on the line finder frame, to battery. Relay 110, upon energizing, closes a cir cuit from battery, through the left winding of relay 109, left winding of relay 107, outer contact of relay 110-to ground. Relay 107 operates and locks through its right winding and inner right contact, conductor 132 to the contact of relay 200. I

The operation of relay 302 closes a circuit from battery, through the winding of updrive magnet '304, middle left contact of relay 302, upper left contact of cam 364, right the control of the updrive magnet 304 the line finder shaft is moved upwards. Due to the operation of the trip magnet 303 the set of brushes serving the group of lines to which line 100 belongs is tripped. When the switch shaft leaves the tripping zone a circuit is closed from ground over brush 307, through commutator segment 305,=upper contacts of cam 306, outer left norfnal contact of key 204, inner right contact and right winding of relay 201 to battery. Relay 201 is held operated in this circuit but the circuit through the locking winding of relay 108 is shunted and that relayreleases, in turn releasing the trip magnet 303. As soon as brush 307 leaves. segment 305 the circuit of relay 201 is o ened and that relay releases again connectmg battery to the operating windings of relay 108 and the corresponding relays in other trip circuits, so. that subsequent calls may be served. s

Relay 302 closes a locking circuit for itself over its inner left contact, right contact of cam 308,-back contact of relay 320, commutator segment 321, brush 322 to ground, which is closed as soon as the line finder shaft moves upward. Relay 302 also closes a circuit from'battery, over the inner left contact of relay 205, right winding of relay 203, conductor 207, left contacts of cam 403, brush 462, and its associated terminal, conductor ,379, upper left contactof cam 311, ri ht front contact of relay 302 to ground. he operation of relay 203 removes ground from conductor 206 thus preventing the starting of another line finder until the brushes are tripped. Relay 203 locks in a circuit from battery, over the outer left contact of relay 205, left winding and outer left front contact of relay 203, left back contact of relay 202, conductor 131, inner right contact of relay. 103, outer left contact of relay 108,

outer contact of relay 110 to ground. The

tact, upper left contact of cam 311, conductor 379, brush 462 and its associated contact, right contact of cam 404, upper left contact of cam 405, right winding of relay 406, winding of relay 407, upper left contact of cam 408, upper right contact of cam 409, resist ance 410 to battery. Relays 406 and 407 operate, relay 406 closing a locking circuit for itself and relay 407 from battery, through resistance 410, upper right contact of cam 409, upper left contact of cam 408, winding of relay 407, right winding of relay 406', contact of cam 411, contact of relay 406 to ground. -Relay 407 operates, closes a circuit from battery, through the winding of sequence switch magnet 400, upper contact of cam 412, contact of relay 407 to round. Magnet 400 operates advancing the link circuit sequence switch to osition 2.

In position 2 groun is connected from the right contact of cam 415 to brush 466 and its associated contact, conductor 375,

403,.conductor 207, right winding of relay 203, inner left contact of relay 205 to battery, holding relay 203 operated until the link cirbeen cuit is moved out of position 1. When the link circuit arrives in position 2 relays 406 and 407 release. The release of relay 407 completes a circuit from ground at the back contact of relay'407, upper right and lower left contacts of cam 405, winding of magnet 487 to battery. Magnet 487 operates and closes an obvious circuit for magnet 488. Magnet 488 is the rotary magnet for sender selector switch 480 and causes the switch to rotate in search of an idle-v sender.

An idle sender is characterized by the connection of battery, through a suitable resistance, such as resistance 501, to conductor 502 and its corresponding terminal in the set engaged by brush 483. With the link circuit sequence switch in position 2 ground is connected over the upper right contact of cam 421, through the left winding of relay 406, lower contact of cam 413, right winding of relay 406, winding of relay 407, lower contact of cam 401, lower right contact of cam 402, to brush 483.

When brush 483 encounters a terminal corresponding to an idle sender, to which battery is connected, relay 406 operates, short circuiting its left hand winding over its contact and the contact of cam 411, permitting relay 407 to operate in series with the right hand winding of relay 406. The operation of relay 407 opens the circuit of magnet 487 and closes a circuit from battery through the winding of sequence switch magnet 400, upper contact of cam 412, front contact of relay 407 to ground, advancing the link sequence switch to position 3.

In position 3 a circuit is prepared extending from ground through the right and middle windings of relay 503, inner left contact of relay 504, right outer back contact of relay 505, conductor 506, brush 484 of sender selector 480, lower left and upper right contacts of cam 408, brush 464 of district finder 460 to conductor 315, left contact of cam 316, left Winding of relay 317 to battery, which circuit is not completed until the district sequence switch reaches position 3.

In the meantime the line finder shaft continues to move upwards until it reaches the terminals corresponding to the calling subscribers line. \Vhen these terminals are encountered a circuit is completed from battery, through the right winding of relay 109 in parallel with resistance 111, inner front contact of line relay 101, conductor 114, terminal 380, brush 381, right contact of cam 318, winding of relay 320 to ground. Relay 320 operates and closes a circuit in. shunt of its winding through resistance 319, right front contact of relay 320, commutator segment 321, brush 322 to ground. Relay 109, which is marginal, is so adjusted as not to operate in the circuit previously traced in series with relay 107 or in the circuit traced for the winding of relay 320. With resistance 319 in parallel with relay 320, however relay 109 does operate. The operation 0 relay 109 opens the locking circuit of relay 110 and relay 110 releases after an interval due to the fact that it is slow to release.

Relay 320 opens the locking circuit of relay 302 and that relay releases as soon as brush 310 encounters an insulating segment on centering commutator 309. The release of relay 302 opens the circuit of updrive magnet 304 and stops the line finder on the calling subscribers line. It also connects battery through resistance 323 and its left back contact, lower right and upper left contacts of cum 324, right inner back contact of relay 317, resistance 325, brush 326 and terminal 327, over conductor 112, windings of cutoff relay 102 to ground. Relay 102 operates and releases line relay 101 thereby removing the calling condition from terminal 380. The release of relay 101 opens the circuit through the right winding of relay 109 permitting its release as soon as relay 110 releases. The release of relay 101 permits relay 103 to release and also opens the initial circuit of relay 320. The connection of battery with terminal 327 marks terminal 113 and the other multipled terminals of calling line 100 in the terminal bank.n of final selectors with reduced battery potential to render the line busy at such final selectors. 'The release of relay 302 closes a circuit from battery through the winding of sequence switch magnet 300, lower left contact of cam 328, outer right front contact of relay 314, right back contact of relay 302 to ground. Sequence switch 300 is advanced in this circuit to position 3.

hen sequence switch 300 leaves position 2 the circuit of relay 314 is opened and that relay releases. WVhen the sequence switch 300 reaches position 3, the previously traced circuit for relays 503 and317 is completed. Relay 317, being marginal, does not operate at this time. Relay 503 operates and closes an obvious circuit for relay 507 which, in turn, closes a circuit from battery, through resistance 508, winding of relay 509, outer left front contact of relay 507 to ground. He-

lay 509 operates and locks over its inner right front contact. Relay 507 closes a circuit for relay 510 from battery, winding of relay 510, conductor 534, to ground, at the inner left front contact of relay 507; The operation'of relay 510 closes an obvious circuit for relay 511 which, in turn, closes a circuit through the right winding of relay 512.

Theoperation of relay 512 opens the circuit previously traced from battery, through resistance 501, to relays 406 and 407 and these relays release. The release of relay 407 closes a circuit from battery, through the windin; of sequence switch magnet 400, lower right contact of cam 412, back contacts of relay 407 to ground. Sequence switch 400 is advanced to position 4 from which position .it is moved position 5 by means of ground over the lower left contact of cam 412.

In position 5 of the link sequence switch the dialing leads and the fundamental circuit leads are cut through directly from the district to the sender circuit. The dialing circuit may be traced from battery, through the left winding of relay 606, conductor 637, normally made contacts of relay 513, sender selector brush 485 and its corresponding terminal, lower contacts of cam 414, district finder brush 465 and its corresponding terminal, conductor 382, lower contact of cam 329, winding of relay 330. right back contact of relay 317, line finder brush 331, terminal 332, conductor 116' through the subscribers substation, conductor 117, terminal 333, brush 334, middle left back contacts of relay 317, left contact of cam 335,- conductor 375, brush 466.and its associated terminal, lower left contact of cam 415, brush 486 and its associated terminal,outer right back contact of 'relay 515, to ground. WVhen the dialing circuit above traced is completed, relay 606 operates and closes a circuit from battery through the winding of relay 610, front con:

tacts of relay 606, conductor 639, inner right back contact of relay 515 to ground. Relay 610 operates and closes a circuit from battery through the winding ofrelay 609, right front contacts of relay 610, conductor 638, upper left contact of cam 516 to ground. As soon as relay 609 operates. the dialing tone circuit is completed as follows: from source of tone 607, right winding of relay 606, normal terminal and brush 804 of switch 800, outermost left contacts of relay 609, lower contactof cam 514, to ground at the inner left front contacts of relay 507.

Due to the closure of this circuit a tone is induced in the left winding of relay 606, Fig. 5 and over the dialing circuit to the receiver of the subscribers telephone to indicate that dialing may be started. The subscriber now dials the assigned long distance code number as the first step in extending his connection to the proper operators position, from which position the connection is then further ex-,

tended to the wanted long distance subscriber.

The operation of the sender in response to the manipulation of the subscribers dial and its consequent operation in causing the district selector to hunt for and connect with an idle trunk to the operators position, are no part of the presentinvention, are completely described in the above identified patent to Kopp, and hence are not included as a part of this description, but reference is made to that patent for a complete description of these omitted operations.

When, in accordance withthe operation described in the above patent, the district selector has connected .with an idle trunk extending the operators position, the district 10 and a trunk closure test is made of the trunk from the sender. The circuit for this test extends from ground, ballast lamp 831, Fig. 8, lower winding of relay 844, top outer back contacts of relay 803, lower left winding of repeating coil 813, bottom outer back contacts of relay 835, conductor 385 and cooperating terminal to brush 355, left upper and right lower contacts of cam 356, conductor 379, brush 462, right upper and lower contacts of cam 404, brush 482 and cooperating terminal, right front contacts of relay 507, left outer back contacts of relay 524, compensating resistance 859, brush 832 of translator 830, contact of cam 525, left winding of relay 704', winding of relay 716, lower contacts of cam 717 outer back contacts of relay 711, right contact of cam 954, left contact of cam 523, right outer back contacts of relay 504, brush 481 and cooperating terminal, left lower and upper right contacts of cam 402, brush 461 and cooperating terminal, conductor 378, left inner back contacts of relay 359, upper contacts of cam 358, brush 357, conductor 386 and connected terminal, upper back contacts of relay 835, Fig. 8, left upper winding of repeating coil 813, top inner back contacts of relay 803, upper winding of relay 844, ballast lamp 842 to battery. Relay 716 operates in this circuit but relays 844 and 704 do not. The operation of relay 716 functions to advance the sender to make the proper talking selection in the district, advancing thedistrict selector sequence switch to position 15 and thereafter to dismiss the sender, all in accordance with the manner disclosed in the above mentioned patent.

With the district selector sequence switch 300 in position 15 a circuit is closed over the above traced battery and ground path in the operators trunk circuit to brushes 357 and 355, respectively, left contacts of cam 358, upper right winding of repeating coil 360, lower contacts of cam 348, winding of relay 361, lower right winding of repeating coil 360, upper contacts of cam 356, brush 355 and thence through the above traced circuit at the operators position, including relay844. The resistance of this circuit is such that the Euantity of current flowing through it is sufcient to operate relay 844, but its direction the district selector should the calling subscriber flash his receiver before the toll oper- III ator answers. Relay 806, in operating, causes the operation of relay 810. Relay 810 closes a circuit from battery through the upper winding of relay 811, upper winding of relay 812, top contacts of relay 810, top inner front contacts of relay 807, right upper winding of repeating coil 813. conductor 814, top back contacts of relay 815, conductor 827, upper left winding of repeating coil 816, top inner back contacts of relay 817, both windings in series of polarized relay 818, bottom back contacts of relay 817, left lower winding of repeating coil 816, conductor 833, bottom back contacts of relay 815, conductor 819, right lower winding of repeating coil 813, bottom inner front contacts of relay 807', bottom contacts of relay 810, lower winding of relay 812, lower winding of relay 811 to ground. Relay 818 operates in this circuit but relay 812 does not operate because the resistance of the circuit is too high and relay 811 does not operate because its windings are differential in respect to the current flowing through the circuit. Relay 818 causes the operation of relay 820 over an obvious circuit and opens, at its back contacts, the lower winding of relay 821. The operation of relay 820 closes a circuit from battery on the top back contacts of relay 823, bottom outer contacts of relay 820, lamp 822 to ground. Lamp 822 lights as an indication that a call is waiting on the trunk.

When the toll operator answers by insertmg the plug of a toll cord circuit, such as is shown in Fig. 9 in the trunk answering jack 824, a circuit is closed from battery through the upper winding of relay 900, conductor 901, sleeves of plug and jack, conductor 825, bottom winding of relay 826, upper winding of relay 821 to ground. Relays 821 and 826 operate in the above circuit. Relay 821 causes the operation of relay 823 over an ob- V ous circuit and this latter relay opens the circuit of lamp 822 thereby extinguishing it. Relay 823, by closing its top outer contacts, connects the left lower winding of repeating coil 816 through condenser 828 and thence to the left upper winding of the said repeating coil and short circuits, through its bottom contacts, the high resistance lower winding of relay 818. Due to the corresponding increase of current in the circuit above traced and including relays 811, 812 and 818, relay 812 operates. Relay 812 in turn causes the operation of relay 829. Relay 829 causes the operation of relay 803 over a circuit from ground on the top contacts of relay 829, bottom inner normally made contacts of relay 803, winding of relay 803 to battery. Relay 803, in operating locks through its bottom inner make contacts to ground on the bottom contacts of relay 806, reverses the direction of current flow in the trunk circuit path above traced and including relay 361 in the district selector. The current flow is now in the proper direction to operate relay 361, which, on operating, closes a circuit for relay 314 from ground over the left contacts of cam 350, front contacts of relay 361, left lower and right upper contacts of cam 347, right winding of relay 314 to battery. Relay 314 operates and closes a circuit from ground over cam 339 and the left lower contact thereof, right outer front contacts of relay 314, left lower contact and cam 328, winding of magnet 300 to battery. The switch magnet operates and advances the sequence switch to position 16 which is the talking to operator position. The operation of relay 803 also 'closes the talking circuit by connecting condenser 843 over its bottom outer contacts, to the two right windings of repeating coil 813.

In position 16. of the district selector sequence switch, the repeating coil is removed from the trunk loop and talking battery is supplied to the calling subscriber from battery through the ballast lamp 842, upper winding of relay 844, thence as traced to the upper right contact of cam 329, thence as traced over the calling loop to cam 335 and the upper contact thereof, thence as traced through the lower winding of relay 844 to ground. Relay 844 now holds over the said loop. In position 16, relay 314 is held locked over a circuit from ground on the bottom front contacts of relay 805, through retard coil 809 to conductor 383 and cooperating terminal, previously described, brush 349, right contacts of cam 350, right inner front contacts of relay 314, left winding of relay 314 to battery. The operation of relay 803 also completes, over its bottom outer contacts, the talking circuit by connecting condenser 843 to the right windings of repeating coil 813 as previously described.

The toll operator now operates talking key 902 and learns from the subscriber that a toll connection is desired. It'is then necessary, before proceeding with steps to extend the subscribers line to the toll area, to check and learn the identity of the calling line number. In order to do this number checking key 604 is operated. Key 604 closes a circuit to operate relay 601. Relay 601 looks over its bottom winding and bottom inner contacts to ground on the bottom outer back contacts of relay 600 and, over its top front contacts, prepares a circuit to operate relay 600 over its bottom winding. It also closes an obvious circuit for lamp 605 which lights. If the common calling line test circuit is idle at this time then the circuit for relay 600 is completed from battery, back contacts of relay 1001, right inner back contacts of relay 1002, right back contacts of relay 1003, conductor 608, bottom winding of relay 600, to ground on the top front contacts of re- My 601. Relay 600 operates and closes a looking path from battery through its top wind- -ing battery for relay 600 and similar relays at other recording or toll positions the lower windings of whose lock-in relays are all connected in parallel to conductor 608. Should an operator at another recording or toll position at this time depress the position checking key to verify a callinglinenumber,then,while the consequent operation of the position relay 601 prepares a path to operate the position cut-in relay 600, yet so long as the test circuit has been locked in with another position by the operation of relay 600 at that position, relay 1001 will be operated in series with the locking winding of relay 600 of that position and operating battery for the cut-1n relays at all other positions is removed at its contacts. Relay 600 of the position to which the test circuit is connected also cuts oil the locking circuit of other relays 600 over its top inner back contacts and, over its bottom outer front contacts, connects ground to conductor 611, operating relays 716 and 724 in parallel. Relay 716 locks over its No. 11 contacts to conductor 718 while relay 724locks over its No. 0 contacts to conductor 718. Conductor 718 is connected through the contacts of release key 607 to ground on the top outer back contacts of relay 601.

The operated relay 600 closes an additional circuit for lamp 605 which continues to glow as long as the test circuit remains connected tothe position. The lamp circuit at relay 600 replaces that at relay 601 which releases when relay 600 operates. Over its top outer contacts, relay 600 connects ground through low resistance 612 to conductor 602 which is connected in parallel to a conductor in each of the position toll cords connecting with a bottom inner contact on talking key 9-02. If the calling line number is being checked, key 902 is operated and the low resistance ground is connected in parallel to the sleeve conductor 901. The shunting parallel circuit reduces the current throu h the circuit of relays 826 and 821 and, relay 826 being marginal, releases. The release of relay 826 removes the shunt around the winding of relay 817 and this relay now operates in a circuit from battery through the top inner front contacts of relay 823, resistance 839, winding of relay 817 to ground. The operation of relay 817 disconnects the winding of relay 818 from the trunk conductors, causing it to release. Belay 820, however, does not release when relay 818 releases since it is held looked over its top outer contacts to ound on the top outer contacts of relay 81%. The operation of relay 817 connects a battery of a higher voltage to the trunk conductors over a path from hattery through the upper winding of retard coil 840, bottom inner front contacts of relay 820, bottom front contacts of relay 817, left lower winding of repeating coil 816, conductor 833,

bottom back contacts of relay 815, conductor 819, right lower winding of relag813, bottom inner front contacts of relay 807 ,bottom contacts of relay 810, bottom winding of relay 812, bottom winding of relay 811 to ground. another circuit is also closed .from ground through the bottom winding of retard coil 840, to inner front contacts of relay 820, top inner ront contacts of relay 817, left upper windin of repeating coil 816, conductor 827, top bac contacts of relay 815, conductor 814, right upper winding of repeating coil 813, top inner front contacts of relay 807, top contacts of relay 810, top winding of relay 812, top winding of relay 811 to battery. ue to the difference in curent flow between the upper and lower windings of relay 811, caused by circuits of diiferent batterytpotentials, the opposing characteristics of the windings of relay 811 are.overcome and sufiicient current flows through the lower winding to overcome the opposing current through the upper winding to causerelay 811 to operate. Relay 811, in turn, causes the operation of relay 808. The operation of relay 808 closes a circuit from ground through the secondary winding of a transformer 841 whose primary is connected to a source of alternating current preferably of high frequency, top outer contacts of relay 808,-sleeve conductor 383 and cooperating terminal, brush 349, right contacts of cam 350, right inner front contacts of relay 314, left contacts of relay 314, right upper and left lower contacts of cam 348, condenser 388, top contacts of cam 368, brush 326, terminal 327, sleeve conductor 112, sleeve terminal 113, corresponding cross connecting terminal 134, to conductor 1004. Conductor 1004 is the test conductor connecting the sleeve circuit of a subscribers line with the calling line test circuit. There is one such conductor from the sleeve terminal of each subscribers line to the test circuit and the distribution of all the said conductors within the test circuit as well as the effects of an alternating potential on the said test conductor of the calling line whose number is being verified will hereinafter be described.

It will be noted that the trunk circuit above described and connecting the district selector with the operators position is one of a well known type which is used when the operators position is located at a distance from the originating central office and in which but two trunk conductors, namely 814 and 819, extend from the said oflice to the said position. Consequently the method of signaling the outgoing end of the trunk from the said position to connect an alternating potential to the sleeve conductor ofthe connection is one specifically adapted to the type of trunk dis- 

